1. Field of the Invention
The present invention relates to circular saws and in particular to clutch assembly positioned between the blade shaft and the shaft rotated by the saw's motor.
2. Scope of the Prior Art
Circular saws use a saw blade to cut materials such as wood. A shaft having a gear or pinion at the distal end that is powered by the saw's motor rotates a blade shaft. Traditionally, the bolt and washer are used to secure the blade into a hole provided in the blade shaft. A wrench is required to tighten the bolt and washer is that the blade remains secured to the shaft. As it can be appreciated, the bolt must be tightened enough to secure the blade for rotation. A user is instructed, however, not to over tighten the bolt and is told to tighten the bolt with the wrench only a one-eighth turn past finger tight. The need to use a wrench can be cumbersome, and it requires that the tool be available.
The material cut by the saw can lock saw blades. Accordingly, the blade will not rotate even though the motor is rotating the shaft and gear. The bolt and washer that secures the blade to the rotating blade shaft therefore functions as a clutch so that the motor does not burn out. If the bolt is over tightened, however, the bolt-and-washer clutch arrangement may not function properly. The saw therefore may tend to kick and the motor may be damaged.
Other power tools that have rotating parts, such as table saws and, power drills etc., also use bolts and other mechanisms to secure the blade or bit to a rotating shaft. These power tools also must protect the motor when the blade or bit is locked. Table saws use the same bolt and washer arrangement. Chucks can be used by other tools such as drills.
It has long been known to use various types of friction-type washers as clutch arrangements for automobiles, agricultural equipment, and other devices. Those clutches drive a member and include an arrangement of Belleville washers and friction plates. When the member is locked, the clutch arrangements allow the motor and engine to continue rotating while the member remains stationary. These clutches tend to be heavy-duty because of the forces involved and the torque required by the equipment.